<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">
        p > strong{
            color: red;  /* unlike descendant selector,only change its child */
        }
    </style>
</head>
<body>
    <p>e.g.<strong>I will change</strong><p>

    <p>e.g. <em><strong>I won't change</strong></em> </p>
</body>
</html>